The purposes of this project are to better understand why some women report daily changes in feeling healthy or ill during their menstrual cycle and to determine if exercise effects how they feel. Participants will report symptoms on the Washington Women's Health Diary every day throughout the study. They will complete two UO2 max exerccise tests during which blood to be analyzed for responses of the neuroendocrine stress axis to challenge. One will be scheduled during the lateral phase of the study and one during the follicular phase.